MAG5035

Been bouncing between -2 and -3ºF this morning here. Temperatures especially in the west and central this morning have ended up pretty close to the modeled temps of the coldest models (Euro/GFS). On the Mesowest network there’s several stations reporting -20 or colder, with a -28 near Slippery Rock. On the Ambient network there’s a -22ºF in the Barrens region SW of State College, a typical optimal radiational cooling spot. Temperatures tonight will likely be even colder overall with more widespread below zero lows.

I just think the phase happens too late, its hard to bring a later developing coastal low off the Carolina coast back in close enough to affect central PA without some kind of a situation where its completely cut off/blocked downstream.. which doesn’t look to be the situation here. The storm deepens rapidly and may retro a bit but then it shoots NE. New Euros doing some kind of dumbbelling type action with the low, which acts to really drive up its snow solution in southern New England. Cold’s probably playing a hand in it too, we’re in a frigid pattern. We’re looking at the potential for some record lows Saturday morning as this storm is just beginning to take shape. The center of the closed 500mb low is all way down over Savannah, GA as the trough rotates negative. That’s a bit too far down for us, the surface low explodes on the Gulf Stream and will likely run up along it.

The only thing really keeping me into this threat to any degree is the 500mb ridge axis in great positioning for C-PA. Otherwise it just looks like the trough is going to swing negative too late and system stays relatively progressive. Looked a little bit further into the CIPS analog stuff and off GFS guidance one of the top analogs for the Northeast/East Coast domain that come up is the Boxing Day 2010 storm, which I think is most the representative analog vs forecast setup of a top 5 that consisted of Jan 2016 and even Jan 1996. That’s why the 90th percentile is off the hook on that analysis. Statistically, those accumulations represent amounts that are higher than 90%+ of the dataset.. the highest outliers in other words. Having those big hitters in the mix also skews the mean as well. Here’s the median snowfall, which indicates a lot of these analogs didn’t produce much of anything. Here’s the mean 500mb vs GFS The mean western ridge axis on the analogs is actually a tad east of what the GFS has, and it’s definitely west of the alignment for the Boxing Day 2010 storm. That storm actually tracked up from the Carolina coast and inside of the benchmark while the general consensus of guidance right now is to take the surface low up from Hatteras outside (southeast) of the benchmark. So I think this certainly has room to trend snowfall back our direction, but I’m fairly doubtful it’ll be enough for C-PA due to the reasons mentioned at the top of the post. The storm gets going too late.

At least we didn’t see this kind of crazy sleet. https://www.wboy.com/pendleton/watch-crews-use-excavators-to-clear-sleet-slides-in-west-virginia-mountains/ Pendleton County, WV

Looks like focus could be starting again on about this time next weekend once everyone rests up haha. The 0z Euro op blasted central and eastern PA tonight. This amplifcation and major, highly anomalous closed 500mb low is notable on all the major ops, but the Euro’s the only one that had this kind of storm solution tonight. 500mb ridge axis out west is lining up in the spot favorable for a coastal to strike C-PA if we can time a phase. So we’ll see what happens with this, plenty of time to reel it in.

Considering we had the kind of mid-level pattern that we did for this storm, I’d say we did extremely well. Here’s 500mb heights and anomalies during the height of the storm today at the 18z initialization of the Euro. And Mesowest 700mb heights and temp advection at 18z today. This drove the mix line and the NAM ended up handling that the best. No closed 700mb low and the 700mb trough was aligned way west. Weaker secondary surface development to the coast wasn’t going to affect this issue. The fact that we had a forum wide warning event with widespread double digits while also being about as cold as you get at the surface for a synoptic event out of the Gulf is pretty remarkable with an alignment like that. At the end of the day this storm was mostly a moisture charged overrunning event with a very strong arctic air mass in place.

I think you’ll see some of it up that way, perhaps an inch or so if the stuff in western PA holds together good. Less sure once south of about Harrisburg, might not see much additional down there. This kind of skirts ENE, and then westerly flow kicks in eventually and that will relegate what’s left to western PA and the Laurels most likely.

Got out and did some measurements with the lull in the action, I’m at 11.6” right now. The comma head stuff is on the doorstep so we’ll see how much additional I can muster. Temp is still only 10ºF. This snow is very powdery but it is also dense, which is typical of Gulf storms. Never mixed but I do think the ratios suffered a bit due to the warm nose. Being so high up that would have affected growth in the 700mb layer which was likely where the best lift was. Given the heavy rates basically all day today this could have easily been more. I did see a couple 13 and 14” totals reported elsewhere in Blair.

Exactly one week ago, haha.

Past the 9” mark now with continued heavy snow rates and temps have torched up to 10ºF.

Back in western PA the mix line is remaining well south of Pittsburgh, generally near the Mason-Dixon line. That then cuts up NE thru Bedford/Fulton to where it’s pressed up into the Sus Valley. The next couple hours are going to be where the max WAA occurs to drive the sleet up into the Sus Valley. I would expect a changeover back to snow to try to work back down thru the LSV eventually as that intense WAA passes and the column starts cooling at that level. However, the big thing by that point is going to be the race between that and the main precip shutting off. Models seem to be timing a mid-evening shutoff (10pm ish). There’s a lot of storm to go.

Thats certainly possible, That 700-800mb area is the only part of the column that warms to the point of mixing and that’s quite high up. We never lose 850mb on down, and there’s plenty of lift at that level as well.

Heaviest snow of the event so far, working on 7”. Temp 9ºF

Past the 4” mark here with moderate to heavy rates. Temp 8ºF

The first heavier band has arrived and it is ripping here..probably working on an inch or so already. Decent flake size and it’s fluff. Temp is down to 9ºF, which is nuts for an event like this.

In Harrisburg?

Surprised no one posted this earlier, CTP bumped up amounts areawide. My point and click is up to 13-21 inches now.

Snow began here just a bit after midnight, light for now. Temp 10ºF, Dewpoint 2ºF. Its happening!

3k NAM does try to bring the snow line back down as the secondary starts to take over, which keeps places like JST and AOO pretty much mostly or all snow but it slots before it really drops back into the Sus Valley. At the same time this model is showing the best comma head over western and northern PA and is probably the snowiest run yet for the max snows, which is exceeding 20” on Kuchera in west central PA. Sleet is prolific in the far PA southern tier/LSV and well, just about everywhere else south of there. This is the kind of setup I feel there’s going to be a zone of multiple inches of sleet somewhere given the depth of the arctic air mass. That widespread? We’ll see. But that’s 2-3” of sleet on top of the 5-7” of snow it puts out in the LSV. Snowfall

1st and probably only call I’m gonna do with this. I could’ve just put a text box that said 10-18” on it and called it a day and would’ve had the model support to defend it. But I am hedging some on the NAM thermals being at least partly right and a bit more sleet intrusion. Not full NAM, but somewhere in between that and the general consensus. These are purely snow numbers, obviously the reduced zones in the southern tier are for sleet mixing, but if that were to occur than sleet accumulations would be fairly notable as well (perhaps an inch or so). The only reason I’m giving the NAM a bit more weight in what is mainly a snowier consensus is strictly its handling of mid-level features and the warm nose. If the snowier consensus wins out, then the whole subforum simply sees 12-18”. Impact wise, that really isn’t that much of a difference.. this is going to be disruptive. I also think top end will be tempered a bit, mainly for speed of the system. Mostly I think there will be a lot of 14s and 15s with some 16-18” reports sprinkled in. It doesn’t look like any kind of a comma head lingers in C-PA to drive widespread amounts toward the 20” mark. What could overcome that is a fast start to the heavier snows when the best snow ratios will be before the mid-levels of the column start to warm later in the event. Both of these points were mentioned in CTP’s disco from yesterday.. which was a good informative discussion.

Oh yea here’s some current obs, it’s half a degree here right now.

Back this way the PSU Walker Building noted 5.8” of snow and 2.8” of sleet on the observation card from that event, and then a further 1.8” of snow on the next day’s observation card. I do remember this storm made quite the glacier pack.

That’s about what the 3k NAM puts out for a large chunk of Virginia into the western Carolinas. Despite getting the mixing further north, it is by no means warm outside of that region near the 800mb level where above freezing air manages to advect in. Which actually brings up the haggling over details that I’m usually trying to sort out for our area, ice impacts. Let’s look down in the Mid-Atlantic region…I’m no fan of whatever algorithm the Euro uses to generate its p-types when it comes to sleet vs freezing rain. Instead of a sleet bomb, it pretty much encases the entire state of Virginia in about .75-1.00” of freezing rain. These two models have a pretty similar column thermally. Here’s Euro’s 925mb (3000 ft temps) Euro 1hr precip/ptype at the same frame That’s with surface temps in the low to mid 20s all the way down thru western NC and 850mb (5000ft) temps below zero in northern VA. No way am I buying that big of an expanse of crippling freezing rain on CAD of that strength and depth there outside of the Apps in the far western part of the state. A much more sleet heavy scenario, with an eventual transition to freezing rain late in the event seems more plausible. But yea those are two models with radically different ice scenarios despite similar column thermals. Applying this to our area, any mix type during the main part of this is going to be sleet. There’s just too much depth to the cold for anything appreciable freezing rain wise.

This storm has definitely sped up a bit both in onset time and ending time now that we’re getting into the near term forecasting of it, which is pretty common with these type of storms. It looks like the business end of this occurs in a bit under 24 hours now, arriving in the LSV approx 2-3am Sunday and starting to shut off midnight-1am or so Monday.

I might do one. Think I at least want to see what the 0z suite offers up first.